Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/release.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository == 'puppetlabs/vmpooler-provider-gce'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Get Current Version
         uses: actions/github-script@v7

.github/workflows/security.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: checkout repo content
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 1
     - name: setup ruby

.github/workflows/testing.yml

@@ -20,7 +20,7 @@ jobs:
         ruby-version:
           - 'jruby-9.4.3.0'
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:
@@ -36,7 +36,7 @@ jobs:
         ruby-version:
           - 'jruby-9.4.3.0'
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with: